The traditional wheel spraying method is to spray the front side of a wheel, with substantially no requirement on back cavity color. In order to meet the requirements of some special vehicles, there are corresponding requirements on the appearance and structure of wheels, and back cavity spraying is one of them. At present, the only way is to spray the wheel with its front side facing downward. However, in terms of product diversity and dimensional diversity, a universal support that satisfies the spraying process requirements has not yet been found.